In the Garden:Coastal and Tropical South
November, 2011
Regional Report

Seek Perennial Perfection

By tending to perennial plants in the fall, you can be sure of more and better performance next year. It is time to plant, dig, divide and rework perennial beds.

Plant the Year
If there is one complaint gardeners voice about perennial plants, it is that they look better at some times of the year than others. One way to approach this problem is to plant the bed or border for a succession of seasonal interest. Start by choosing your favorite color, such as purple and select plants that will display it throughout the year. A different strategy relies on the so-called seasonal colors with emphasis on pink and blue in spring, red and purple in summer, and classic yellow, orange and rust in the fall. By planting the bed or border so these seasonal bloomers are equally dispersed, each season and plant gets its due. Use grasses and tall perennials like butterfly bush to fill spaces and gaps in color and to give the seasonal plants a dramatic backdrop no matter the season. Take advantage of the wide availability of perennials to plant, including those you propagate yourself.

When to Cut Back
Some perennial plants grow all year in parts of our regions, and their maintenance should be done as needed. You can prune to limit growth, remove old flowers and damaged stems, but also to rejuvenate them. Every few years, even evergreen perennials need to be cut back entirely or dug up and divided before replanting.

Gardeners are of two minds when it comes to removing browned stems on perennials that go dormant. I agree with those who say it is better to let the stems die back completely before cutting them down. Others clip off the browned parts as they develop to keep the plants looking neater, and I have done that on occasion when company was coming. You can keep perennials looking good with the simple regime of grooming during their growing season and dividing them as needed to keep new leaves and flowers coming.

Garden tradition dictates digging, dividing, and replanting in the season opposite bloom time, but our seasons allow for a wider range. For example, verbena and dianthus can put on flowers in any month. You can divide them in the fall or spring, but my experience leads me to prefer fall because the weather is more agreeable for me and the plants. Most perennials can be divided after three years, but some, like Shasta daisies, put on their best shows when they are divided annually. Hostas are notorious for slow growth, and it may be four or five years before their clumps are thick enough to warrant dividing.

Keep Beds Clean
Sanitation is key to preventing pest problems in perennial plants. The term simply means to keep the garden clean to reduce food sources and hiding places where insects and diseases can lurk.
Here are some examples of sanitation tasks you can do in the fall.

Get in the habit of cutting flowers before each rainy day. Cooler temperatures often follow autumn rainstorms and can put the flowers in perfect shape to develop nasty Pythium fungus. If they are in a vase, you can enjoy them and prevent the ugly, gray masses that form on the flowers. Once the spores are unleashed, flowers in the area will be more likely to encounter them in future seasons.

After a rain, pull or dig up the weeds in and around garden beds to reduce hiding places for insects. Always remove garden debris promptly, and inspect plants regularly to watch for signs of insects or disease. It is tempting to let leaves fall into the bed because they will eventually rot. A better practice is to blow them off the mulch and into the compost heap so they cannot become hiding places insects, their eggs and larvae. Finally, use a light oil spray annually on dormant perennial crowns to smother any pests lurking in the crevices.